The experiments outlined in this proposal are designed to directly reveal the suspected presence and nature of any trophic and inductive influences in the etiology of muscular dystrophy. To analyze this question wing buds and spinal cords will be transplanted between normal and dystrophic chick embryos. Thus, genetically, predetermined normal or dystrophic muscle will develop with genetically predetermined dystrophic or normal nervous innervation respectively. The anatomical and physiological properties of neuromuscular junctions from these operated muscles will be examined through development to maturity. To accomplish these ends, I intend to study the electrophysiological properties of nerve terminals under direct visual control. These same identified junctions will then be fixed in place and selectively stained for subsequent light and electron microscopy. These experiments are specifically designed (1) to provide direct evidence for and neural influence in the etiology of muscular dystrophy, (2) to gain a better knowledge of how neuronal trophic effects manifest themselves and influence their normal postsynaptic structures, and (3) to broaden our knowledge of retrograde trophic influences exerted by the dystrophic muscles on the motor neurons innervating them.